Harnessing Orbital-to-Spin Conversion of Interfacial Orbital Currents for Efficient Spin-Orbit Torques

Area of Science:

• Spintronics
• Materials Science
• Condensed Matter Physics

Background:

• Current-induced spin-orbit torques (SOTs) are crucial for electrical manipulation of magnetism in spintronic devices.
• Enhancing SOT efficiency is key, typically achieved by maximizing spin accumulation or modulating spin density.
• A net spin accumulation is fundamental for generating current-induced torques.

Purpose of the Study:

• To investigate the significant enhancement of SOT efficiency in thulium iron garnet (TmIG)/Pt heterostructures.
• To explore the underlying physical mechanisms responsible for the observed SOT efficiency increase.
• To demonstrate a novel method for boosting torque generation in spintronic devices.

Main Methods:

• Fabrication of TmIG/Pt heterostructures capped with a CuOₓ layer.
• Characterization of SOT efficiency using electrical measurements at room temperature.
• Analysis of spin and orbital current transport phenomena at interfaces.

Main Results:

• A colossal enhancement of SOT efficiency by a factor of 16 was observed for 1.5 nm of Pt.
• The enhancement is attributed to an interfacial orbital current generated at the CuOₓ/Pt interface.
• This orbital current is converted to a spin current in Pt, exerting a nonlocal torque on TmIG.

Conclusions:

• Capping TmIG/Pt with CuOₓ dramatically increases SOT efficiency.
• The findings suggest a significant role for orbital currents in spintronic torque generation.
• This work provides insights into orbital transport and offers a path toward highly efficient spintronic devices.